1. Field of the Invention
The present invention relates to a wafer scale lens used for an image-pickup optical system and an optical system having the same. More particularly, the present invention relates to an optical system which can achieve superior optical capability using a diffraction surface and a refractive surface.
2. Description of the Related Art
In general, mobile phones had only communicative functions in their recipient stage. However, with extensive use of the mobile phones, the services required therefrom have been diverse including camera function, image transmission, and telecommunication. Thus, the functions and the services of mobile phones have been constantly evolving. In the meantime, a new concept of mobile phones has been popularized these days, in which digital camera and mobile phone have been merged in technology. They are so called camera phones or camera mobile phones. In addition, so called camcorder mobile phones or camcorder phones have been developed recently, in which digital camcorder technology is incorporated into mobile phone technology, thereby allowing saving and transmitting multi-media moving pictures of more than tens of minutes.
Besides the mobile phones, with computers being popularized, PC cameras have become available in a short period of time for video chatting or video conferencing. Meanwhile, still cameras have been quickly substituted with digital cameras.
These cameras are typically required to be small and light-weight due to their characteristics. Thus, conventional optical systems with plastic or glass lens have been used, but this is limited in miniaturization.
In order to overcome such a problem, a “replica method” has been proposed, in which a plurality of lenses are provided in a single lens substrate to form an optical system. However, this method is limited in the thickness of polymer formed on the lens substrate, posing difficulty in realizing an efficient optical system.